The presently disclosed embodiments relate generally to methods for the removal of coatings from an imaging member for use in electrostatographic, including digital, apparatuses. More particularly, the embodiments pertain to a method for stripping the electrophotographic imaging layers from an electrophotographic imaging member using ultra-high pressure water.
Electrophotographic imaging members, e.g., photoreceptors, typically include a photoconductive layer formed on an electrically conductive substrate. The photoconductive layer is an insulator in the substantial absence of light so that electric charges are retained on its surface. Upon exposure to light, the charge is dissipated.
In electrophotography, also known as xerography, electrophotographic imaging or electrostatographic imaging, the surface of an electrophotographic plate, drum, belt or the like (imaging member or photoreceptor) containing a photoconductive insulating layer on a conductive layer is first uniformly electrostatically charged. The imaging member is then exposed to a pattern of activating electromagnetic radiation, such as light. The radiation selectively dissipates the charge on the illuminated areas of the photoconductive insulating later while leaving behind an electrostatic latent image. This electrostatic latent image may then be developed to form a visible image by depositing oppositely charged particles on the surface of the photoconductive insulating layer. The resulting visible image may then be transferred from the imaging member directly or indirectly (such as by a transfer or other member) to a print substrate, such as transparency or paper. The imaging process may be repeated many times with reusable imaging members.
An electrophotographic imaging member may be provided in a number of forms. For example, the imaging member may be a homogeneous layer of a single material such as vitreous selenium or it may be a composite layer containing a photoconductor and another material. In addition, the imaging member may be layered. These layers can be in any order, and sometimes can be combined in a single or mixed layer. Typical multilayered photoreceptors or imaging members have at least two layers, and may include a substrate, a conductive layer, an optional charge blocking layer, an optional adhesive layer, a photogenerating layer (sometimes referred to as a “charge generation layer,” “charge generating layer,” or “charge generator layer”), a charge transport layer, an optional overcoating layer and, in some belt embodiments, an anticurl backing layer. These layers are usually formed by a coating process such as dip coating or spraying. Electrophotographic imaging members are commonly utilized in electrophotographic (xerographic) processes in either a flexible belt or a rigid drum configuration. Other members may include flexible intermediate transfer belts that are seamless or seamed, and usually formed by cutting a rectangular sheet from a web, overlapping opposite ends, and welding the overlapped ends together to form a welded seam.
Presently, photoreceptors can be salvaged for reuse if the various electrophotographic imaging layers can be removed from the substrate. Various methods are typically employed for separating the photosensitive layer(s), blocking layer, adhesive layer, and any other layers typically employed in a photoreceptor from the substrate. These methods include cutting the electrophotographic imaging layer from the substrate; exfoliating the coating layer by repeated heating and cooling; heating the coating layer followed by chemical treatment; and heating the coating layer under vacuum to vaporize it. Each of the known methods, however, has residual problems. For example, these removal processes are labor intensive, require an inordinate amount of manufacturing space, and may involve heat and solvents which undesirably damage the underlying substrate. Some of the methods may also evolve dust or emit harmful vapors or poisonous substances and may use environmentally incompatible solvents, thus contributing to the pollution of the environment. Many times, these processes are extremely costly, and often it is more cost effective to sell the photoreceptor as scrap.
In addition to removing the various electrophotographic imaging layers, electrophotographic imaging members having a drum configuration require additional removal steps. For example, drum type photoreceptors are usually supported on an electrically conductive shaft by hubs or end flanges. Often the hub or end flange is secured to the end of the drum by a resin adhesive. In order to clean and recycle the used or defective photoreceptor, the hubs or end flanges must be removed, and the resin adhesive must be stripped off the photoreceptor. Such removal techniques may damage the underlying substrate, may involve complex equipment and is time intensive, and may involve solvents which require special handling and disposal.
Thus, there is a need for a method that facilitates removal of the electrophotographic imaging layers from a substrate which reduces the need for extensive physical manipulation of the photoreceptor, which reduces pollution, which reduces the area dedicated to photoreceptor salvage, which reduces the need to scrap an otherwise functional photoreceptor, and which is faster and relatively less costly to implement than conventional removal methods. There is also a need for a method that facilitates removal of the electrophotographic imaging layers from a substrate so that the substrate can be reused to form new imaging members. Reclaiming the substrate from a photoreceptor is a highly desirable alternative to depositing an otherwise functional photoreceptor in metal reclamation facilities and landfills. In addition, the ability to remove a defective or damaged electrophotographic imaging layer from a substrate without damaging the substrate so that the substrate can be recoated lowers the manufacturing costs of imaging members.
The term “photoreceptor” or “photoconductor” is generally used interchangeably with the terms “imaging member.” The term “electrostatographic” includes “electrophotographic” and “xerographic.” The terms “charge transport molecule” are generally used interchangeably with the terms “hole transport molecule.”